The important contribution of various polycyclic aromatic hydrocarbons to carcinogenic potency of complex mixtures has been demonstrated. Whether the complex mixture is from petroleum, coal, shale oil, or automobile exhaust, the investigation of metabolic fate of these compounds is an important step towards understanding their carcinogenic action. Most of the previous metabolism work has dealt with benzo(a)pyrene. However, it has been shown that neutral basic fractions of complex mixtures contain heterocyclic nitrogen-containing compounds that have considerable carcinogenic potency for the lungs of experimental animals. In fact, dibenzo(c,g)carbazole appears to be a stronger respiratory tract carcinogen than benzo(a)pyrene. At present, there has not been any work done on the metabolism of N-heterocyclics. Therefore, the objective of this proposed research will be to investigate the metabolism of an environmental pollutant from a complex mixture, dibenzo(c,g)carbazole, using an isolated perfused lung under various experimental conditions that influence its carcinogenic potency. The clarification and understanding of how certain environmental factors, known to enhance the carcinogenic response by heterocyclic aromatics and cause formation of certain metabolites and changes in the metabolic pathway, will contribute heavily to the study of the mechanism of bronchiogenic carcinoma.